High density polyurethane and polyisocyanurate construction boards and composite boards

ABSTRACT

A construction board comprising a cellular body including at least one planar surface, where the cellular body includes a polyurethane or polyisocyanurate cellular structure, where the cellular structure has a density greater than about 2.5 pounds per cubic foot, an ISO index of at least 270, and where the cellular body includes at least 5.0% by weight flame retardant based on the weight of the cellular body.

This application claims the benefit of U.S. Provisional Application No.60/898,353, filed Jan. 30, 2007, which is incorporated herein byreference.

FIELD OF THE INVENTION

The present invention is directed toward high density polyurethane orpolyisocyanurate construction boards and composite boards, as well astheir use in flat or low-slope roofing systems.

BACKGROUND OF THE INVENTION

Flat or low-slope roofs are often covered with multi-layered roofingsystems. These roofing systems often include a roof deck, an insulationlayer, and a protective, weather-resistant membrane. In some situations,a coverboard is also employed. In many situations, insulation boards aretypically adhered directly to a roof deck, which is most commonlyconstructed of concrete or steel. These insulation boards are typicallyclosed-cell foams that include polyurethane or polyisocyanurate cellularmaterials with an insulating gas trapped within the cells. Theinsulation boards are then covered with the weather resistant membrane.

The foam insulation boards are typically low density cellularstructures. The low density stems from two primary considerations. Thefirst is cost because lower density cellular structures employ lessmaterial. Also, and often more important, the insulation value of theboard can be improved with lower density structures. While a density ofzero would be ideal (i.e., a vacuum), a certain degree of cellularstructure—which gives rise to the density—is required to maintain theintegrity of the insulation boards. Particularly, a foam core density ofgreater than about 1.5 pounds per cubic foot (pcf) (7.323641 kg/m²) isneeded to maintain strength, and a core density of less than about 2 pcf(9.764855 kg/m²) is conventional for cost and insulation considerations.

Coverboards typically include fiber boards, gypsum products such asdensdeck, and perlite boards. Coverboards are typically used to addintegrity to the roof. For example, especially where improved fireperformance is sought, the coverboard may first be applied to the steeldeck, the insulation board is applied on top of the coverboard, and themembrane is then applied over the insulation board. Alternatively,especially where the roof may experience heavy traffic, the insulationboard may be applied to the roof deck, the coverboard applied over theinsulation board, and then the membrane is applied over the coverboard.In the latter situation, the coverboard obviously provides protection tothe insulation board, which is prone to denting or damage due to thefact that the insulation boards are low density cellular materials.

Coverboards are also extensively used in re-roofing situations. In theseapplications, the coverboard may be referred to as a “re-coverboard.” Aswith residential roofs, flat or low-slope roofs can be re-roofed withoutremoving or “tearing off” the existing roofing membrane. In manyinstances, the re-coverboard is first applied to the existing roofingmembrane before a new roofing membrane is applied to the roof. Also, anadditional layer of insulation board can be applied before the newmembrane is applied. Depending upon the result desired, there-coverboard can be applied above or below the insulation board.

In other instances, a composite board is employed in lieu of (orpossible in addition to) the coverboard and insulation board. Thecomposite boards include an insulation layer together with a layer thatis rather robust such as a wood fiber, gypsum, or perlite board. Oneadvantage of the composite board is the ease of installation. In otherwords, rather than apply both an insulation board and a coverboard, thecomposite board can simply be installed in a one-step process. Otheradvantages have been observed based upon the fact that the compositeboard is formed integrally within a controlled environment (i.e., thefactory).

The use of construction boards in new roofing systems and re-roofsituations is, therefore, technologically important therebynecessitating further advancement in the field.

SUMMARY OF THE INVENTION

Certain embodiments are directed toward a covered low-slope or flat roofcomprising a roof deck, an optional insulation board including apolyurethane or polyisocyanurate cellular structure having a densitythat is less than 2.5 pounds per cubic foot (12.20607 kg/m²), acoverboard including a polyurethane or polyisocyanurate cellularstructure, where the cellular structure has a density greater than about2.5 pounds per cubic foot, an ISO index of at least 270, and includes atleast 5.0 weight percent flame retardant based on the weight of thecellular structure and a membrane.

Other embodiments are directed toward a method of re-roofing a low-slopeor flat roof, the method comprising applying a re-coverboard to anexisting covered low-slope or flat roof, wherein the re-coverboardincludes a polyurethane or polyisocyanurate cellular structure, wherethe cellular structure has a density greater than about 2.5 pounds percubic foot, an ISO index of at least 270, and includes at least 18 partsby weight flame retardant per 100 parts by weight polyol and applying amembrane to the re-coverboard subsequent to the step of applying are-coverboard.

Other embodiments are directed toward a construction board comprising acellular body including at least one planar surface, where the cellularbody includes a polyurethane or polyisocyanurate cellular structure,where the cellular structure has a density greater than about 2.5 poundsper cubic foot, an ISO index of at least 270, and where the cellularbody includes at least 5.0% by weight flame retardant based on theweight of the cellular body.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary perspective view of a high-density constructionboard of the present invention.

FIG. 1A is a fragmentary perspective view of another high-densityconstruction board of the present invention.

FIG. 2 is a fragmentary perspective view of a roofing system including ahigh density coverboard.

FIG. 3 is a fragmentary perspective view of a roofing system including ahigh density coverboard.

FIG. 4 is a fragmentary perspective view of a roofing system includingre-roof layers.

FIG. 5 is a fragmentary perspective view of a roofing system includingre-roof layers.

FIG. 6 is a fragmentary perspective view of a composite constructionboard of the present invention.

FIG. 6A is a fragmentary perspective view of another compositeconstruction board of the present invention.

FIG. 6B is a fragmentary perspective view of still another compositeconstruction board of the present invention.

FIG. 6C is a fragmentary perspective view of still yet another compositeconstruction board of the present invention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

One or more embodiments of the present invention are directed toward ahigh density polyurethane or polyisocyanurate cellular constructionboards. The unique high density characteristics of these boards allowthem to be advantageously used in the construction of new flat orlow-sloped roofs, as well as in re-roofing situations. In other words,these construction boards are useful as coverboards or re-coverboards.In one or more embodiments, the construction boards advantageously meetrequirements imposed by UL-790 for flame spread. In these or otherembodiments, the construction boards include a hydrocarbon blowing agentwithin the cells of the boards.

A high density board according to one or more embodiments is depicted inFIG. 1. Board 10 includes a cellular body 11 having a planar shape withfirst planar surface 12 and second planar surface 14, each defined by alength 16 and a width 18. Board 10 may also be characterized by athickness 20. Length 16 and width 18 of board 10 may vary, and theseembodiments are not necessarily limited by the selection of a particularlength or width. Nonetheless, because these boards are advantageouslyemployed in the construction industry, board 10 may be sized to a 4′×8′sheet (e.g., 3.75′×7.75′), a 4′×10′ sheet, or a 4′×4′ sheet. Thethickness 20 of the board can generally be greater than about 0.255inches (0.65 cm), in other embodiments greater than about 0.30 inches(0.76 cm), in other embodiments greater than about 0.375 inches (0.95cm), and in other embodiments greater than about 0.40 inches (1.01 cm).In these or other embodiments, the thickness 20 may be from about 0.375to 2.0 inches (0.95-5.08 cm) or in other embodiments from about 0.38 to0.75 inches (0.97-1.91 cm) in thickness.

Board 10 may include an optional facer 22, which can be positionedadjacent one of the first or second planar surfaces 12 or 14. Forexample, as shown in FIG. 1, facer 22 may be positioned adjacent secondplaner surface 14. A planar interface may exist between cellular body 11and at least one facer 22.

Facer 22 may include a variety of materials or compositions, many ofwhich are known or conventional in the art. Useful facers include thosecomprising aluminum foil, cellulosic fibers, reinforced cellulosicfibers, craft paper, coated glass fiber mats, uncoated glass fiber mats,chopped glass, and combinations thereof. Useful facer materials areknown as described in U.S. Pat. Nos. 6,774,071, 6,355,701, RE 36674,6,044,604, and 5,891,563, which are incorporated herein by reference.The thickness of the facer material may vary; for example, it may befrom about 0.01 to about 1.00 inches thick (0.025-2.54 cm) or in otherembodiments from about 0.015 to about 0.050 inches thick (0.04-0.13 cm),or in other embodiments from about 0.015 to about 0.030 inches thick(0.04-0.07 cm). The facer materials can also include more robust orrigid materials such as fiber board, perlite board, or gypsum board. Thethickness of the rigid facer can vary; for example, the thickness of therigid facer can be from about 0.2 to about 1.5 inches (0.51-3.8 cm), orin other embodiments from about 0.25 to about 1.0 inches (0.64-2.54 cm).

As shown in FIG. 1A, board 10 may also optionally include a facer 23positioned adjacent the planer surface opposite the planar surface onwhich facer 22 is positioned. For example, facer 22 is positionedadjacent second planer surface 14, and facer 23 is positioned adjacentfirst planer surface 12. Facer 23 can include the same or differentmaterials or compositions, as well as the same or different thickness asfacer 22.

Also, as noted above, facers 22 and 23 are optional. Therefore, in oneor more embodiments, board 10 may be facerless. The ability to producefacerless construction boards is known as described in U.S. Pat. No.6,117,375, which is incorporated herein by reference.

Body 11 includes a polyurethane or polyisocyanurate cellular structure,which may include an interconnected network of solid struts or platesthat form the edges and faces of cells. These cellular structures may,in one or more embodiments, also be defined by a “relative density” thatis less than about 0.8, in other embodiments less than 0.5, and in otherembodiments less than 0.3. As those skilled in the art will appreciate,“relative density” refers to the density of the cellular materialdivided by that of the solid from which the cell walls are made. As therelative density increases, the cell walls thicken and the pore spaceshrinks such that at some point there is a transition from a cellularstructure to one that is better defied as a solid containing isolatedpores.

Despite the cellular nature of body 11, it has a high density. In one ormore embodiments, the density of body 11 is greater than 2.5 pounds percubic foot (12.2 kg/m²), as determined according to ASTM C303, in otherembodiments the density is greater than 2.8 pounds per cubic foot (13.7kg/m²), in other embodiments greater than 3.0 pounds per cubic foot(14.6 kg/m²), and still in other embodiments greater than 3.5 pounds percubic foot (17.1 kg/m²); on the other hand, in one or more embodiments,the density of body 11 may be less than 20 pounds per cubic foot (97.6kg/m²), in other embodiments less than 10 pounds per cubic foot (48.8kg/m²), in other embodiments less than 6 pounds per cubic foot (29.3kg/m²), in other embodiments less than 5.9 pounds per cubic foot (28.8kg/m²), in other embodiments less than 5.8 pounds per cubic foot (28.3kg/m²), in other embodiments less than 5.7 pounds per cubic foot (27.8kg/m²), in other embodiments less than 5.6 pounds per cubic foot (27.3kg/m²), and still in other embodiments less than 5.5 pounds per cubicfoot (26.9 kg/m²).

In one or more embodiments, body 11 is characterized by an ISO Index, asdetermined by PIR/PUR ratio as determined by IR spectroscopy usingstandard foams of known index (note that ratio of 3 PIR/PUR provides anISO Index of 300), of at least 270, in other embodiments at least 285,in other embodiments at least 300, in other embodiments at least 315,and in other embodiments at least 325. In these or other embodiments,the ISO Index is less than 360, in other embodiments less than 350, inother embodiments less then 340, and in other embodiments less than 335.

In one or more embodiments, body 11 includes a flame retardant contentof at least 5.0 wt %, in other embodiments at least about 5.5 wt %, inother embodiments at least about 5.75 wt %, in other embodiments atleast about 6.0 wt %, in other embodiments at least about 6.25 wt %, andin other embodiments at least about 6.3 wt %, where the wt % is basedupon the total weight of a given sample of the cellular body (i.e. thefoam). In these or other embodiments, the flame retardant content isless than about 15 wt %, in other embodiments less than about 10 wt %,and in other embodiments less than about 8 wt %.

In one or more embodiments, body 11 and at least one of the facers (e.g.facer 22) are intimately bonded along their interface as a result of theprocess by which the construction board is formed. For example, in oneor more embodiments, the developing foam may contact the facer,partially diffuse into or be absorbed by the facer, and cure, whichthereby bonds cellular body 11 to the facer. This bond may include amechanical bond, a chemical bond, or both a chemical and mechanicalbond. Where the at least one facer 22 includes cellulose material, achemical bond may be formed between the cellular body and the faceralong their interface. Despite the relatively high ISO Index of cellularbody 11, the bond between at least one facer 22 and cellular body 11 maybe characterized by a tensile strength of at least 3.5 psi, in otherembodiments at least 5.0 psi, and in other embodiments at least 6.0 psias determined by ASTM method C 209 Tensile Strength perpendicular tosurfaces using 250° F. (121.1111° C.) hot melt adhesive systems.

The boards of one or more embodiments of this invention can be generallymanufactured by using known techniques for producing polyurethane orpolyisocyanurate insulation In general, processes for the manufacture ofpolyurethane or polyisocyanurate insulation boards are known in the artas described in U.S. Pat. Nos. 6,117,375, 6,044,604, 5,891,563,5,573,092, U.S. Publication Nos. 2004/01099832003/0082365, 2003/0153656,2003/0032351, and 2002/0013379, as well as U.S. Ser. Nos. 10/640,895,10/925,654, and 10/632,343, which are incorporated herein by reference.

In one or more embodiments, the boards of the present invention may beproduced by developing or forming polyurethane and/or polyisocyanuratefoam in the presence of a blowing agent. The foam may be prepared bycontacting an A-side stream of reagents with a B-side stream of reagentsand depositing the mixture or developing foam onto a laminator carryinga facer. The A-side stream may include an isocyanate compound and theB-side may include an isocyanate-reactive compound.

In one or more embodiments, the A-side stream may only contain theisocyanate. In other embodiments, the A-side stream may also containflame-retardants, surfactants, blowing agents and othernon-isocyanate-reactive components.

Suitable isocyanates are generally known in the art. In one or moreembodiments, useful isocyanates include aromatic polyisocyanates such asdiphenyl methane, diisocyanate in the form of its 2,4′-, 2,2′-, and4,4′-isomers and mixtures thereof, the mixtures of diphenyl methanediisocyanates (MDI) and oligomers thereof known in the art as “crude” orpolymeric MDI having an isocyanate functionality of greater than 2,toluene diisocyanate in the form of its 2,4′ and 2,6′-isomers andmixtures thereof, 1,5-naphthalene diisocyanate, and 1,4′diisocyanatobenzene. Exemplary isocyanate components include polymericRubinate 1850 (Huntsmen Polyurethanes), polymeric Lupranate M70R (BASF),and polymeric Mondur 489N (Bayer).

The B-side stream, which contains isocyanate reactive compounds, mayalso include flame retardants, catalysts, emulsifiers/solubilizers,surfactants, blowing agents, fillers, fungicides, anti-staticsubstances, water and other ingredients that are conventional in theart.

An exemplary isocyanate-reactive component is a polyol. In one or moreembodiments, polyols or polyols components include diols, polyols, andglycols, which may contain water as generally known in the art. Primaryand secondary amines are suitable, as are polyether polyols andpolyester polyols. Useful polyester polyols include phthalic anhydridebased PS-2352 (Stepen), phthalic anhydride based polyol PS-2412(Stepen), teraphthalic based polyol 3522 (Kosa), and a blended polyol TR564 (Oxid). Useful polyether polyols include those based on sucrose,glycerin, and toluene diamine. Examples of glycols include diethyleneglycol, dipropylene glycol, and ethylene glycol. Suitable primary andsecondary amines include, without limitation, ethylene diamine, anddiethanolamine. In one embodiment, a polyester polyol is employed. Inone or more embodiments, the present invention may be practiced in theappreciable absence of any polyether polyol. In certain embodiments, theingredients are devoid of polyether polyols.

Catalysts are believed to initiate the polymerization reaction betweenthe isocyanate and the polyol, as well as a trimerization reactionbetween free isocyanate groups when polyisocyanurate foam is desired.While some catalysts expedite both reactions, two or more catalysts maybe employed to achieve both reactions. In one or more embodiments,useful catalysts include salts of alkali metals and carboxylic acids orphenols, such as, for example potassium octoate; mononuclear orpolynuclear Mannich bases of condensable phenols, oxo-compounds, andsecondary amines, which are optionally substituted with alkyl groups,aryl groups, or aralkyl groups; tertiary amines, such aspentamethyldiethylene triamine (PMDETA),2,4,6-tris[(dimethylamino)methyl]phenol, triethyl amine, tributyl amine,N-methyl morpholine, and N-ethyl morpholine; basic nitrogen compounds,such as tetra alkyl ammonium hydroxides, alkali metal hydroxides, alkalimetal phenolates, and alkali metal acholates; and organic metalcompounds, such as tin(II)-salts of carboxylic acids, tin(IV)-compounds,and organo lead compounds, such as lead naphthenate and lead octoate.

Surfactants, emulsifiers, and/or solubilizers may also be employed inthe production of polyurethane and polyisocyanurate foams in order toincrease the compatibility of the blowing agents with the isocyanate andpolyol components.

Surfactants may serve two purposes. First, they may help toemulsify/solubilize all the components so that they react completely.Second, they may promote cell nucleation and cell stabilization.Exemplary surfactants include silicone co-polymers or organic polymersbonded to a silicone polymer. Although surfactants can serve bothfunctions, a more cost effective method to ensureemulsification/solubilization may be to use enoughemulsifiers/solubilizers to maintain emulsification/solubilization and aminimal amount of the surfactant to obtain good cell nucleation and cellstabilization. Examples of surfactants include Pelron surfactant 9920,Goldschmidt surfactant B8522, and GE 6912. U.S. Pat. Nos. 5,686,499 and5,837,742 are incorporated herein by reference to show various usefulsurfactants.

Suitable emulsifiers/solubilizers include DABCO Kitane 20AS (AirProducts), and Tergitol NP-9 (nonylphenol+9 moles ethylene oxide).

In one or more embodiments, useful flame retardants includetri(monochloropropyl) phosphate (a.k.a. tris(cloro-propyl) phosphate),tri-2-chloroethyl phosphate (a.k.a tris(chloro-ethyl) phosphate),phosphonic acid, methyl ester, dimethyl ester, and diethyl ester. U.S.Pat. No. 5,182,309 is incorporated herein by reference to show usefulblowing agents. In one or more embodiments, the flame retardant employedin the practice of the present invention is a liquid at standardconditions of temperature and pressure (e.g. 25° C. and 1 atm).

In one or more embodiments, useful blowing agents include hydrocarbons.In other embodiments, useful blowing agents include fluorinatedhydrocarbons. Exemplary blowing agents include isopentane, n-pentane,cyclopentane, alkanes, (cyclo)alkanes, hydrofluorocarbons,hydrochlorofluorocarbons, fluorocarbons, fluorinated ethers, alkenes,alkynes, carbon dioxide, and noble gases.

In one or more embodiments, the equivalent ratio of isocyanate groups toisocyanate-reactive groups introduced to prepare the developing foam isat least 2.7:1, in other embodiments at least 2.85:1, in otherembodiments at least 3.0:1, in other embodiments at least 3.15:1, and inother embodiments at least 3.25:1. In these or other embodiments, theequivalent ratio of isocyanate groups to isocyanate-reactive groups isless than 3.6:1, in other embodiments less than 3.5:1, and in otherembodiments less than 3.4:1. As those skilled in the art appreciate, theequivalent ratio refers to ratio of the number of moles of isocyanategroups in a given weight of isocyanate reactant to the number of molesof isocyanate-reactive groups in a given weight of isocyanate-reactivereactant. Stated another way, the equivalent ratio is a molar ratio ofisocyanate groups in a given weight of A-side stream toisocyanate-reactive groups in a given weight of B-side stream that isintroduced and mixed to form the developing foam.

Other reactants employed may be described with reference to the amountof polyol (e.g. per 100 parts by weight polyol (php)). Depending on thehydroxyl content of the polyol, the NCO content of the isocyanate, andthe amount of water in the reactants, the amounts may vary. Accordingly,the amounts of the reactants provided for herein are with reference tothe ingredients conventionally employed, which are generallycharacterized as follows: the polyols typically have a hydroxyl contentor hydroxyl number (KOH/g of polyol) of from about 230 to about 250; theisocyanates typically have an NCO content or isocaynate value of about30 to about 32, and the ingredients typically contain about 0.25 toabout 0.50 parts by weight of water per 100 parts by weight polyol.Hydroxyl content may be determined by acetylation with pyridine andacetic anhydride in which the result is obtained as the differencebetween two titrations with KOH solution; the hydroxyl value may bedefined as the weight of KOH in milligrams that will neutralize theacetic capable of combining by acetylation with one gram of the polyol.NCO content refers to the weight percentage of reactive —NCO groups.While the foregoing ranges are provided to give guidance to thoseskilled in the art, the same should not be understood as limitinginasmuch as construction boards having the advantageous characteristicsof this invention can be prepared by using ingredients having distinctcharacteristics.

In view of the foregoing, in one or more embodiments, the foam reactants(i.e. the A-side and/or B-side) employed to produce the developing foam(i.e. foam giving rise to the cellular body) of the construction boardsof the present invention may include at least 10 parts by weight flameretardant, in other embodiments at least 15 parts by weight flameretardant, in other embodiments at least 18 parts by weight flameretardant, and in other embodiments at least 20 parts by weight flameretardant per 100 parts by weight polyol. In these or other embodiments,the foam reactants (i.e. the A-side and/or B-side) employed to producethe developing foam of the construction boards of the present inventionmay include less than 50 parts by weight flame retardant, in otherembodiments less than 40 parts by weight flame retardant, in otherembodiments less than 30 parts by weight flame retardant, and in otherembodiments less than 25 parts by weight flame retardant per 100 partsby weight polyol.

In one or more embodiments, the foam reactants (i.e. the A-side and/orB-side) employed to produce the developing foam of the constructionboards of the present invention may include at least 20 parts by weightblowing agent, in other embodiments at least 8 parts by weight blowingagent, in other embodiments at least 7 parts by weight blowing agent,and in other embodiments at least 6 parts by weight blowing agent per100 parts by weight polyol. In these or other embodiments, the foamreactants (i.e. the A-side and/or B-side) employed to produce thedeveloping foam of the construction boards of the present invention mayinclude less than 8 parts by weight blowing agent, in other embodimentsless than 7 parts by weight blowing agent, in other embodiments lessthan 6 parts by weight blowing agent, and in other embodiments less than5.5 parts by weight blowing agent per 100 parts by weight polyol.Depending on the required density of the board, the amount of blowingagent may need to be decreased up to about 95% from a standardformulation. The amount of water may also, optimally, be reduced. Theless blowing agent used, the less catalyst is generally used.

In one or more embodiments, the foam reactants (i.e. the A-side and/orB-side) employed to produce the developing foam of the constructionboards of the present invention may include at least 10 parts by weightcatalyst, in other embodiments at least 15 parts by weight catalyst, inother embodiments at least 18 parts by weight catalyst, and in otherembodiments at least 20 parts by weight catalyst per 100 parts by weightpolyol.

In one or more embodiments, the cellular construction boards of thepresent invention are formed using a laminator. The higher density andpotentially higher foam expansion pressure may necessitate higherhydraulic clamping pressure to maintain uniform board thickness and tomove the product down the laminator. In one or more embodiments, theconstruction boards are produced by contacting the A-side and B-sidestreams within a mix head. The pressure at which the A-side and B-sideare contacted within the mix head may be in excess of 2,000 psi (140.6kg/cm²), in other embodiments in excess of 2,100 psi (147.6 kg/cm²), inother embodiments in excess of 2,200 psi (154.7 kg/cm²), and in otherembodiments in excess of 2,400 psi (168.7 kg/cm²). In particularembodiments, the temperature of the B-side ingredients or mixture isincreased to at least 86° C., in other embodiments at least 88° C., inother embodiments at least 90° C., and in other embodiments at least 92°C. immediately prior to entry into the mix head.

As noted above, the high density polyurethane or polyisocyanurate boardsof this invention may be employed in the construction of new roofingstructures and thereby form a unique flat or low-slope roofing system.For example, FIGS. 2 and 3, respectively, show unique roofing systems 30and 31 that employ high density board 10. Furthermore, although the highdensity board 10 depicted in FIGS. 2 and 3 does not include facers,facers can be used.

As shown in FIG. 2, roofing system 30 includes a roof deck 32 havinginsulation board 34 disposed thereon, high density board 10 positionedon optional insulation board 34, and a water-protective layer ormembrane 36 disposed on top of high density board 10. In an alternateembodiment, as shown in FIG. 3, roofing system 31 includes roof deck 32with high density board 10 disposed thereon. Insulation board 34 ispositioned on high density board 10, and water protective layer ormembrane 36 is disposed on top of optional insulation board 34.

The particular embodiment shown in FIG. 2 is advantageous on roofs thatexperience high traffic and/or heavy loads. High density board 10 can befairly robust and durable, and therefore protects insulation board 34from damage. As those skilled in the art will appreciate, thelow-density nature of insulation board 34 makes it susceptible todamage, particularly through denting, when it is mechanically impingedsuch as by pedestrian or vehicle traffic, or by objects falling andcontacting the roof. Also, the embodiment shown in FIG. 2 mayadvantageously reduce flame propagation in exterior fire tests such asUL 790 or ASTM E108.

Practice of this invention is not limited by the selection of anyparticular roof deck. Accordingly, the roofing systems of thisembodiment, as shown in FIGS. 2 and 3, can include a variety of roofdecks. Exemplary roof decks include concrete pads, steel decks, woodbeams, and foamed concrete decks.

Practice of this invention is likewise not limited by the selection ofany particular insulation board. As is known in the art, severalinsulation materials can be employed. In one embodiment, the insulationboard comprises polyurethane or polyisocyanurate cellular material.These insulation boards are known in the art as disclosed in U.S. Pat.Nos. 6,117,375, 6,044,604, 5,891,563, 5,573,092, U.S. Publication Nos.2004/01099832003/0082365, 2003/0153656, 2003/0032351, and 2002/0013379,as well as U.S. Ser. Nos. 10/640,895, 10/925,654, and 10/632,343, whichare incorporated herein by reference. In general, polyurethane ischaracterized by having an index of from about 100 to about 120;polyisocyanurate is generally characterized by having an index that isin excess of 150 (in other embodiments at least 175, and in otherembodiments at least 200; and insulation with an index between 120 and150 generally includes a mix of polyurethane and polyisocyanurate.

In those embodiments where the insulation layer comprises polyurethaneor polyisocyanurate cellular material, these cellular materials aredefined by a foam density (ASTM C303) that is less than 2.5 pounds percubic foot (12 kg/m²), in other embodiments less than 2.0 pounds percubic foot (9.8 kg/m²), in other embodiments less than 1.9 pounds percubic foot (9.3 kg/m²), and still in other embodiments less than 1.8pounds per cubic foot (8.8 kg/m²). In one or more embodiments, thesepolyurethane or polyisocyanurate insulation layers are likewisecharacterized by having a density that is greater than 1.50 pounds percubic foot (7.32 kg/m²) and optionally greater than 1.55 pounds percubic foot (7.57 kg/m²).

Practice of this invention is likewise not limited by the selection ofany water-protective layer or membrane. As is known in the art, severalmembranes can be employed to protect the roofing system fromenvironmental exposure, particularly environmental moisture in the formof rain or snow. Useful protective membranes include polymericmembranes. Useful polymeric membranes include both thermoplastic andthermoset materials. For example, and as is known in the art, membraneprepared from poly(ethylene-co-propylene-co-diene) terpolymer rubber orpoly(ethylene-co-propylene) copolymer rubber can be used. Roofingmembranes made from these materials are well known in the art asdescribed in U.S. Pat. Nos. 6,632,509, 6,615,892, 5,700,538, 5703,154,5,804,661, 5,854,327, 5,093,206, and 5,468,550, which are incorporatedherein by reference. Other useful polymeric membranes include those madefrom various thermoplastic polymers or polymer composites. For example,thermoplastic olefin (i.e., TPO), thermoplastic vulcanizate (i.e., TPV),or polyvinylchloride (PVC) materials can be used. The use of thesematerials for roofing membranes is known in the art as described in U.S.Pat. Nos. 6,502,360, 6,743,864, 6,543,199, 5,725,711, 5,516,829,5,512,118, and 5,486,249, which are incorporated herein by reference. Inone or more embodiments, the membranes include those defined by ASTMD4637-03 and/or ASTM D6878-03.

Still in other embodiments, the protective membrane can includebituminous or asphalt membranes. In one embodiment, these asphaltmembranes derive from asphalt sheeting that is applied to the roof.These asphalt roofing membranes are known in the art as described inU.S. Pat. Nos. 6,579,921, 6,110,846, and 6,764,733, which areincorporated herein by reference. In other embodiments, the protectivemembrane can derive from the application of hot asphalt to the roof.

Other layers or elements of the roofing systems are not excluded by thepractice of this invention. For example, and as is known in the art,another layer of material can be applied on top of the protectivemembrane. Often these materials are applied to protect the protectivemembranes from exposure to electromagnetic radiation, particularly thatradiation in the form of UV light. In certain instances, ballastmaterial is applied over the protective membrane. In many instances,this ballast material simply includes aggregate in the form of rock,stone, or gravel; U.S. Pat. No. 6,487,830, is incorporated herein inthis regard.

The high density boards are also advantageously useful in re-roofsituations. In other words, and as is known in the art, an existing roofcan be re-roofed without the need to remove one or more of the existinglayers of the existing roof system. Indeed, a secondary roofing systemcan be applied directly over the existing roofing system. In theseinstances, it is advantageous to apply a “re-coverboard” over theexisting roof before application of another protective membrane. Incertain instances, a second layer of insulation (i.e., a recoverinsulation layer) may also be applied. The additional layer ofinsulation can be applied above or below the re-coverboard, andtherefore the protective membrane is either applied to the re-coverboardor the recover insulation layer. The high-density boards of thisinvention are advantageously applied in re-roofing situations as arecovery board.

For example, one embodiment is shown in FIG. 4, which includes anoriginal roofing system 50 and a re-roof system 51. In a mannerconsistent with that described above, existing roof 50 includes roofdeck 52, insulation layer 54, protective membrane 56, and ballastmaterial 58. Disposed on existing roof 50 is re-roof system 51, whichincludes high density re-coverboard 60, recover protective membrane 64,and ballast material 68. As noted above, high density re-coverboard 60is consistent with the high density boards described hereinabove withrespect to the new roof construction. The nature of this high densityboard advantageously allows it to be used as a re-coverboard. That is,re-coverboard 60 can be applied directly to an existing roof. The robustnature of re-coverboard 60 advantageously allows it to be applieddirectly to material such as ballast material 58.

In other embodiments, the re-coverboard 60 of this embodiment can beapplied directly to an existing roofing membrane. For example, and asshown in FIG. 5, re-coverboard 60 and protective membrane 64 can form are-roof system 51 on top of an existing roofing system 53, whichincludes existing roof deck 52, existing insulation layer 54, andexisting protective membrane 56.

In another embodiment, a composite construction board is provided. Inone embodiment, this composite board can advantageously be employed inthe manufacture of new construction roofing systems. In otherembodiments, the composite boards can advantageously be employed inre-roof situations. In general, the composite boards include one or morehigh density layers and one or more low density layers. They may alsooptionally include one or more facers or one or more reinforcing layerssuch as reinforcing scrims. The positioning of the various layers andfacers can advantageously be varied based upon the intended use orproperties that are desired.

One embodiment of the composite construction board is shown in FIG. 6. Acomposite board 80 includes high density layer 82, low density layer 84positioned underneath high density layer 82, and an optional facer 86.The positions of high density layer 82 and low density layer 84 mayoptionally be reversed. That is, rather than the configuration ofcomposite board 80 shown in FIG. 6, low density layer 84, as shown inFIG. 6A, can instead be positioned above high density layer 82.

Furthermore, additional facers may optionally be positioned between highdensity layer 82 and low density layer 84 and/or optionally bepositioned on the side of composite board 80 opposite optional facer 86.For example, as shown in FIG. 6B, composite board 80 includes anoptional facer 87 positioned between high density layer 82 and lowdensity layer 84, and another optional facer 88 positioned on the sideof composite board 80 opposite optional facer 86. Furthermore, compositeboard 80 can also be configured to include an optional reinforcing layerpositioned between two or more of the various layers. For example, asshown in FIG. 6C, a fiberglass mat 89 is positioned between two optionalfacers 87, 87′ which are positioned between high density layer 82 andlow density layer 84.

Additionally, composite board 80 can be constructed of a plurality ofalternating high density layers and low density layers. For example,composite board 80 may include four layers, where each layer alternatesbetween high density and low density layers. Furthermore, compositeboard 80 could be constructed of three alternating layers where a highdensity layer is sandwiched between two low density layers, or where alow density layer is sandwiched between two high density layers. Eitherway, like the other embodiments discussed above, composite board 80includes at least one high density layer 82 and at least one low densitylayer 84. Moreover, these layers can interface with one another, orfacers can be provided therebetween.

As with the high density construction boards of the first embodiment,high density layer 82 of composite board 80 may be characterized byhaving a density that is greater than 2.5 pounds per cubic foot (12kg/m²), in other embodiments greater than 3.0 pounds per cubic foot (14kg/m²), and still in other embodiments greater than 3.5 pounds per cubicfoot (17 kg/m²); on the other hand, the density of high density layer 82may be less than 20 pounds per cubic foot (97.6 kg/m²), in otherembodiments less than 10 pounds per cubic foot (48.8 kg/m²), and stillin other embodiments less than 6 pounds per cubic foot (29.3 kg/m²) Lowdensity layer 84 can be characterized by having a foam density that isless than 2.5 pounds per cubic foot (12.2 kg/m²), in other embodimentsless than 2.0 pounds per cubic foot (9.76 kg/m²), in other embodimentsless than 1.9 pounds per cubic foot (9.28 kg/m²), and still in otherembodiments less than 1.8 pounds per cubic foot (8.79 kg/m²). In one ormore embodiments, these polyurethane or polyisocyanurate insulationlayers may likewise be characterized by having a density that is greaterthan 1.50 pounds per cubic foot (7.32 kg/m²) and optionally greater than1.55 pounds per cubic foot (7.57 kg/m²).

In one or more embodiments, high density layer 82 and low density layer84 are cellular in nature. In other words, these layers arecharacterized by an interconnected network of solid struts or platesthat form the edges and faces of cells. In one or more embodiments, thecellular material comprises polyisocyanurate or polyurethane.

When present, the optional facers (e.g., 86, 87, 88) can be formed froma variety of materials. Exemplary facer materials include aluminum foil,cellulosic fibers, reinforced cellulosic fibers, craft paper, coatedglass fiber mats, uncoated glass fiber mats, chopped glass, andcombinations thereof. Useful facer materials are known as described inU.S. Pat. Nos. 6,774,071, 6,355,701, RE 36674, 6,044,604, and 5,891,563,which are incorporated herein by reference. The thickness of the facermaterial may vary; for example, it may be from about 0.010 to about0.100 inches thick (0.0254-0.254 cm) or in other embodiments from about0.015 to about 0.050 inches thick (0.0381-0.127 cm). The facer materialscan also include more robust or rigid materials such as fiber board,perlite board, or gypsum board. In one or more embodiments, the facer isa 100% glass facer.

The thickness of the rigid facer can vary; for example, the thickness ofthe rigid facer can be from about 0.20 to about 1.50 inches (0.5-3.8cm), or in other embodiments from about 0.25 to about 1.00 inches(0.6-2.54 cm). When present, the optional reinforcing layers can includea variety of materials. In one or more embodiments, fiber scrims or matscan be employed. These mats and scrims may include woven and non-wovenconstructions. The fibers may include fiberglass or synthetic materialssuch as polyethylene or nylon.

In one or more embodiments, high density layer 82 and low density layer84 comprise the same or similar material. As a result, there is littleinterfacial tension between the layers, which provides an advantageousstrength. In one or more embodiments, high density layer 82 and lowdensity layer 84 are integral with one another as a result of themanufacture and process. In other words, the composite board 80 can bemanufactured by forming low-density layer 84 on top of high densitylayer 82, and the optional facer 86 can thereafter be selectivelyapplied to low density layer 84 (FIG. 6) and/or high density layer 82(FIG. 6A).

In one or more embodiments, high density layer 82 and low density layer84 can be prepared by employing techniques known in the art for theproduction of cellular polyurethane or polyisocyanurate constructionboards. As noted above, the methods are known in the art as disclosed inU.S. Pat. Nos. 6,117,375, 6,044,604, 5,891,563, 5,573,092, U.S.Publication Nos. 2004/01099832003/0082365, 2003/0153656, 2003/0032351,and 2002/0013379, as well as U.S. Ser. Nos. 10/640,895, 10/925,654, and10/632,343 which are incorporated herein by reference.

In one embodiment, the high density cellular body is first formed usingtechniques described above. In one particular embodiment, a facer ispositioned above and below the high density layer. Following themanufacture of this high density board, a low density layer is formedthereon (i.e., the low density layer is formed on one of the facerspositioned on the high density layer) using techniques known in the art.In one particular embodiment, a facer can then be positioned on top ofthe low density layer (i.e., on the planar surface of the low densitylayer that is opposite to the high density layer). In one or moreembodiments, this manufacturing technique can occur within a continuousoperation or production line.

In other embodiments, a high density cellular body or layer can beformed with optional facers. In a second manufacturing step, a lowdensity layer or cellular body can be formed with optional facers. Thehigh density layer (with optional facers) and low density layer (withoptional facers) can be adhered together to form the compositestructure. Optionally, a reinforcement can be positioned therebetween.Conventional adhesives may be employed to adhere the boards to oneanother. In one or more embodiments, the adhesive may include a one-partor two-part polyurethane or polyisocyanurate adhesive. In otherembodiments, a hot-melt adhesive may be employed. Exemplary hot-meltadhesives include polyolefin and polydiolefin-based hot-melt adhesives.

The composite boards can be sized to a variety of dimensions. Ingeneral, composite boards 80 are planar in nature and, as shown in FIG.6, can be characterized by including a length 90, a width 91, and aheight or thickness 92. Because the composite boards are advantageouslyemployed in the construction industry, they may advantageously be sizedto a four foot width and eight foot length (i.e., 4′×8′), other usefulsizes may include 4′×10′ and 4′×4′. As for the overall thickness of thecomposite board, the respective thicknesses of the high-density layersand low-density layers can vary and therefore the overall thickness canvary. Likewise, the thickness of the facer employed, if any, willlikewise contribute to the overall thickness of the composite board. Inany event, the thickness of the composite boards of one or moreembodiments can advantageously be from about 1.0 to about 6.0 inches(2.5-15 cm), or in other embodiments from about 1.5 to about 5.0 inches(3.8-13 cm), or in other embodiments from about 2.0 to about 4.5 inches(5.1-11 cm). In certain embodiments, the thickness of the high-densitylayer can vary from about 0.5 to about 2.0 inches (1.3-5 cm), in otherembodiments from about 0.5 to 1.0 inches (1.3-2.5 cm), and still inother embodiments from about 0.50 to about 0.75 inches (1.3-1.9 cm). Thelow-density layer, in one or more embodiments, can also vary from about0.5 to about 4.0 inches (1.6-10 cm), and in other embodiments from about1.0 to about 4.0 inches (2.5-10 cm), and still in other embodiments fromabout 2.0 to about 4.0 inches (5-10 cm).

In order to demonstrate the practice of the present invention, thefollowing examples have been prepared and tested. The examples shouldnot, however, be viewed as limiting the scope of the invention. Theclaims will serve to define the invention.

EXAMPLES

The following formulation was used to make approximately 0.5 inch (1.57cm) thick high density boards on a commercial laminator.

TABLE I Stepen polyol 2352 100.0 parts by weight  Tri(chloropropyl)phosphate, Supnesta, 20.0 parts by weight Fynol PCF Pelron9540A, Potassium Octanoate (15%) 3.50 parts by weight Water 0.50 partsby weight Pelron Pelsil Surfactant 9920 2.00 parts by weight AirProducts Polycat 5 0.93 parts by weight Conoco Phillips 55/45isopentane/n-Pentane 5.70 parts by weight Huntsman Rubinate 1850, Index3.30 parts by weight

The resulting board was tested and gave the following physicalproperties.

TABLE II Compressive strength, psi 89.8 Core Density, pcf 5.75 BoardDensity, pcf 8.25 Thickness, in. 0.458 Flexural Strength, MachineDirection, psi 383 Flexural Strength, Cross Machine Direction, psi 218

In the wind uplift test at 16 fasteners per board (4′×8″) it failed 27seconds in to the 120 psf (585.9 kg/m²) in the first test and passed 120psf (586 kg/m²) in the second test. At 32 fasteners per board (4′×8′) inthe wind uplift test, the board achieved 24 seconds in to the 240 psf(1172 kg/m²).

This board also passed the UL 290 test using 45 mil EPDM.

Various modifications and alterations that do not depart from the scopeand spirit of this invention will become apparent to those skilled inthe art. This invention is not to be duly limited to the illustrativeembodiments set forth herein.

1. A covered low-slope or flat roof comprising: (a) a roof deck; (b) anoptional insulation board including a polyurethane, a polyisocyanurate,or a mix of polyurethane and polyisocyanurate cellular structure havinga density that is less than 2.5 pounds per cubic foot; (c) a coverboardincluding a polyurethane, a polyisocyanurate, or a mix of polyurethaneand polyisocyanurate cellular structure, where the cellular structurehas a density greater than about 2.5 pounds per cubic foot, an ISO indexof at least 270, and includes at least 5.0 weight percent flameretardant based on the weight of the cellular structure; and (d) amembrane.
 2. A method of re-roofing a low-slope or flat roof, the methodcomprising: (a) applying a re-coverboard to an existing coveredlow-slope or flat roof, wherein the re-coverboard includes apolyurethane, a polyisocyanurate, or a mix of polyurethane andpolyisocyanurate cellular structure, where the cellular structure has adensity greater than about 2.5 pounds per cubic foot, an ISO index of atleast 270, and includes at least 18 parts by weight flame retardant per100 parts by weight polyol and (b) applying a membrane to there-coverboard subsequent to the step of applying a re-coverboard.
 3. Themethod of claim 2, further comprising the step of applying an insulationboard, wherein the insulation board includes a polyurethane, apolyisocyanurate, or a mix of polyurethane and polyisocyanurate cellularstructure having a density of less than 2.5 pounds per cubic foot.
 4. Acomposite construction board comprising: a cellular body including atleast one planar surface, where the cellular body includes apolyurethane, a polyisocyanurate, or a mix of polyurethane andpolyisocyanurate cellular structure, where the cellular structure has adensity greater than about 2.5 pounds per cubic foot, an ISO index of atleast 270, and where the cellular body includes at least 5.0% by weightflame retardant based on the weight of the cellular body; and at leastone facer adjacent to said at least one planar surface. 5.-7. (canceled)8. The roof of claim 1, where the coverboard meets standards for flamespread as provided by UL
 790. 9. The roof of claim 1, where the cellularstructure has an ISO index of at least 285 and includes at least 5.5% byweight flame retardant based on the weight of the cellular structure.10. The roof of claim 9, where the cellular body has an ISO index of atleast 300 and includes at least 6.0% by weight flame retardant based onthe weight of the cellular structure.
 11. The method of claim 2, wherethe re-coverboard meets standards for flame spread as provided by UL790.
 12. The method of claim 2, where the cellular structure has an ISOindex of at least 285 and includes at least 5.5% by weight flameretardant based on the weight of the cellular structure.
 13. The methodof claim 12, where the cellular structure has an ISO index of at least300 and includes at least 6.0% by weight flame retardant based on theweight of the cellular structure.
 14. The composite construction boardof claim 4, where the composite meets standards for flame spread asprovided by UL
 790. 15. The composite construction board of claim 4,where the cellular body has an ISO index of at least 285 and includes atleast 5.5% by weight flame retardant based on the weight of the cellularbody.
 16. The composite construction board of claim 15, where thecellular body has an ISO index of at least 300 and includes at least6.0% by weight flame retardant based on the weight of the cellular body.17. The roof of claim 1, where the coverboard has a first planar surfaceand a second planar surface, said first planar surface and said secondplanar surface having at least one facer positioned adjacent thereto.18. The method of claim 2, where the re-coverboard has a first planarsurface and a second planar surface, said first planar surface and saidsecond planar surface having at least one facer positioned adjacentthereto.
 19. The roof of claim 1, where the coverboard has a thicknessof at least about 0.255 inches.
 20. The roof of claim 19, where thecoverboard has a thickness of at least about 0.375 inches and less thanabout 2.0 inches.
 21. The roof of claim 20, where the coverboard has athickness of at least about 0.38 inches and less than about 0.75 inches.22. The composite construction board of claim 4, where the facer isformed from a material selected from a group of materials includingcoated glass fiber mats, uncoated glass fiber mats, and chopped glass.23. The composite construction board of claim 4, where the compositeincludes at least one low density layer including a polyurethane, apolyisocyanurate, or a mix of polyurethane and polyisocyanurate cellularstructure having a density that is less than 2.5 pounds per cubic foot.24. The composite construction board of claim 23, where the high densitylayer and low density layer comprise the same or similar material. 25.The composite construction board of claim 23, where the compositeincludes a plurality of alternating high density layers and low densitylayers.
 26. The composite construction board of claim 4, where the highdensity layer has a thickness of at least about 0.5 inches and less thanabout 2.0 inches.
 27. The composite construction board of claim 23,where the low density layer has a thickness of at least about 0.5 inchesand less than about 4.0 inches.
 28. The composite construction board ofclaim 25 where the composite has a total thickness of at least about 1.0inches and less than about 6.0 inches.